A further reduction in size of electric elements has been desired along with a reduction in size and an increase in density of devices. A nanostructure represented by functional organic molecules and nanoparticles has been extensively studied. It is considered to be effective to utilize the properties of the nanostructure for electric elements in order to reduce the size of the elements. Therefore, extensive studies on the nanostructure have been conducted by research institutes, companies, and the like. For example, an element has attracted attention which utilizes two electrodes separated by a minute gap (such a pair of electrodes may be hereinafter referred to as “nanogap electrodes”) and the gap is filled with functional organic molecules. For example, Science, 289 (2000) 1172 to 1175 discloses an element catenane molecules are disposed in the gap between nanogap electrodes formed using platinum. This document describes that the catenane molecules undergo an oxidation-reduction reaction by applying a voltage between the electrodes to enable a switching operation.
As the nanogap electrodes, an element in which the gap is filled with nanoparticles has also attracted attention. For example, Nature, 433 (2005) 47 to 50 discloses an element in which nanogap electrodes are formed using silver sulfide and platinum and silver particles are disposed in the gap between the electrodes. According to this document, when a voltage is applied between the electrodes, the silver particles expand or contract due to an electrochemical reaction so that the electrodes can be connected or disconnected to enable a switching operation.
The above-mentioned switching elements require that special synthetic molecules or a complicated metal complex is disposed between the nanogap electrodes. Since these switching elements have a mechanism which utilizes an intramolecular chemical reaction or a reaction between different atoms, these switching elements have dependence on the direction of the applied voltage. This limits utilization of these switching elements. Moreover, since a chemical reaction is utilized for a switching operation, the element tends to deteriorate.
When forming the above-mentioned switching elements, it is difficult to sufficiently reduce the gap between the nanogap electrodes. JP-A-2005-79335 discloses a method of producing nanogap electrodes in which the gap between the nanogap electrodes is reduced, for example.